Motor fuel from wax



June 25, 1940. E, w THlELE 2,205,607

MOTOR FUEL FROM WAX Filed Oct. 26, 1938 RECT/FY/NG COLUMN CATALYST CHAMEER-S E 13 H ATE/2 INVENTOR g Ernest z fgle QMfi M ATTORNEY Patented June 25,1940

UNITED STATES PAT-ENT' OFFICE ard Oil Company, Chicago, 111.,

diana oIIn a corporation Application October 26, 1938, Serial No. 236,969

5 Claims.

This invention relates to the production of high quality motor fuel from paraffin wax by a process of catalytic cracking.

In the manufacture of lubricating oils and 5 paraffin distillates more'wax is produced than is required for known commercial uses. In many parts of the world naturally-occurring waxes are plentiful, although there is an insufficient amount of petroleum to satisfy motor fuel requirements. Various synthetic processes, such for intsance as the Fischer process for converting carbon monoxide and hydrogen into parairinic compounds, yield large quantities of paraflin wax. The object of my invention is to convert this wax into high quality motor fuel. 7

A further object of the invention is to produce a motor fuel with better antiknock characteristics than can be obtained by the thermal or catalytic cracking of other charging stocks. A further object is to obtain large quantities of C5 hydrocarbons for blending with motor fuels for use in cold weather. A further object is to provide a more eflicient method for converting wax into motor fuels and to obtain larger yields of higher 05 quality motor fuels than have heretofore been obtained even by catalytic cracking processes. Other objects will be apparent as the detailed description of the invention proceeds.

Numerous efforts have been made to convert wax into more valuable products. Wax has been cracked thermally but thegasoline components have been characterized by a low antiknock value. Wax has been cracked with aluminum chloride and other metal halides, particularly for the production of lubricating oils, but this type of catalytic cracking is of an entirely different nature than the type to which my invention relates. I seek to avoid the production of high molecular weight compounds and compounds of high parafllnicity. My object is to produce low molecular weight compounds ranging from C4 to Ca hydrocarbons, and to produce highly branched chain hydrocarbons, i. e. hydrocarbons which will be characterized by a very high octane number. The type of cracking, the catalyst and conditions employed, and the results obtained are entirely different than those of previous methods of wax conversion.

In my research work on catalytic cracking a 50 wide variety of stocks was studied, ranging from straight-run naphtha to heavy reduced crude. It was found that straight-run naphthas, paraffin distillates and reduced crudes were all. less desirable than conventional gas oil charging stocks, and it has been assumed by those skilled a per hour.

in the art that the wax present in the paraffin distillates and reduced crudes tended to foul the catalyst and impair the conversion. To investigate this question,'-a 125-12'7 F. melting point paramn wax was catalytically cracked under the same conditions that gas oil had been cracked, and it was discovered that phenomenal results were obtained. The once-'thru yield of gasoline under identical operating conditions" was more than twice that obtained from gas 011. Further- 10 more, the ultimate gasoline yield is significantly higher from wax than from gas oil,as much' as by catalytically cracking wax contained large 20 quantities of propylene and butylenes and the gasoline produced contained exceptionally large quantities of branched chain hydrocarbons. At the same time the carbon deposition on the'catalyst was no more than that obtained by conven- 26 tional gas oil cracking and was far less-than that obtained by gas oil cracking for the same gasoline yields. The rate of cracking was much higher than that for cracking gas oil. Thus it was discovered that catalytic cracking of wax produces new and unexpected results of farreaching importance. V

In practicing the invention I heat wax to a temperature of. about-850 to 1000 F. and contact it with a catalyst at about atmospheric pressure with a space velocity of about A.; to 4 volumes The catalyst is preferably an acidtreated clay of the type used for the decolorization of lubricating oils. (Super Filtrol is a product of this type.) Various acid-treated clays, silica gel impregnated with various oxides etc. may be used instead of Super Filtrol, as will hereinafter be more fully described. After the contact with catalyst the reaction products are fractionated by conventional methods. This simple process on a once-thrubasis produces 40% pr a gasoline having a Reid vapor pressure of about 19 pounds per square inch and an octane number of 88 C. F. R. motor method.

The invention will be more clearly understood fromthe following detailed description and from the accompanying drawing which forms a part of this specification, and which diagrammatically illustrates the catalytic wax-cracking process.

The charging stock for the process is preferably difficult to utilize. The wax may be a naturallyoccurring product such as ceresin. It may be produced from brown coal tars, from the produots obtained by hydrogenating carbonaceous materials, from shale oils, from carbon monoxidehydrogen synthesis or from any other source. Many of these waxes are contaminated with oil and it is unnecessary that all of this oil be removed therefrom, but the wax content of the charge should be at least 35% or higher in order to obtain the advantages of the process. I will describe the invention as applied to the processing of a 125-127 F. melting point parailln wax, but it should be understood that the invention is equally applicable to other waxes.

The wax is melted and pumped as a liquid through line It by pump i I into coils i! of pipe still ll wherein the wax is heated to a temperature of about 850 to 1000" F., preferably 925 F. At this temperature and at a pressure of about atmospheric to 50 pounds per square men the vaporized wax is passed through transfer line It and one or more of the lines I! into one or more of a plurality of catalyst chambers it. These chambers may be of any conventional type and may consist of simple towers with catalysts held in separate beds on screens or foraminous plates. Similarly, a moving type catalyst bed may be used wherein the catalyst continuously or intermittently flows through a tube or chamber, preferably countercurrent to the flow of hot vapors. The particular type of catalyst chamber forms no part of the present invention' and it will not be described in further detail.

The catalyst itself is preferably an acid-treated clay of the type heretofore used for the decolorization of lubricating oils. The clay is treated with acid in a conventional manner, washed with water and made into pellets about V; of an inch in diameter and about of an inch high, these pellets then being dried at temperatures of about 850 to 1000 F.

The composition of this catalyst may vary widely, but I prefer to use those containing relatively large amounts of alumina. The ratio of silica to alumina is preferably about 3.3 by weight or 5.6 mols. of silica to 1 mol. of alumina.

Instead of acid-treated clay I may use catalysts of the silica gel type, particularly silica gel impregnated with alumina or with small amounts of oxides of cerium, thorium, cadmium or copper. Oxides of titanium, manganese or nickel have also been found to give good results on the silica gel-alumina catalyst. No novelty is claimed in these catalysts per se since they are known for the cracking of gas oil. My invention is based on the discovery that a metal oxide catalyst, particularly a catalyst of .the siliceous type gives remarkably new and unexpected results when used for the catalytic cracking of wax.

preferably employ a space velocity of 2, but it may vary from about to about 4, higher space velocities being employed at higher temperatures. A space velocity of 2 means that the amount of charging stock per hour measured as a liquid is twice the volume of the empty space occupied by the catalyst. In the case of catalysts in the tubes, this volume is that of the unfilled tubes. In the case of chambers, the volume is that of the empty chambers less the spaces above and below each catalyst bed.

The length of run is preferably from about minutes to 10 hours, preferably about 1 to 5 hours. After each such run the feed stock is diverted into a different catalyst chamber and the catalyst in the first chamber is regenerated, as will be hereinafter described. For maximum efllciency I prefer to employ runs of about 1 to 5 hours, although the run may be as short as 10 minutes, or may be as long as 10 hours or longer. [in-outstanding feature of the cracking of wax is the high gasoline yields obtained after relatively long runs, or the high yields which are obtained at high space velocities.

The reaction products leave the catalyst chambers through one or more of the lines l1 and are conducted by line II to a suitable fractionating system shown in the drawing as rectifying column is, which is provided with suitable reflux means and reboiler means 2|. C4 and lighter hydrocarbons are taken overhead through line 22, the gasoline fraction withdrawn as a side stream through line 28 and stripped in a conventional side stream strimer, and a gas oil fraction is withdrawn from the base of the tower through line 24. It should be understood that any other fractionation means may be employed instead of, or in addition to the simple rectifying column ii. For instance, column ll may separate gasoline and lighter hydrocarbons overhead, and these overhead fractions may be withdrawn to a gaso line stabilizer for removing the butane and lighter hydrocarbons therefrom. The butane and lighter fractions from the stabilizer may then be passed to a de-ethanizer for removing hydrogen, methane, ethane and ethylene from C: and C4 hydrocarbons, which may in turn be passed to suitable polymerisation, alkylation or gas reversion systems. An important feature of the invention is the large quantity of C: and C1 hydrocarbons produced, and the high unsaturation of these hydrocarbons. These C: and C4 hydrocarbons or the unsaturated components thereof may be introduced with the charging stock to the pipe still or separately heated and passed thru the catalyst chamber with the vaporized wax to effect gas reversion, thereby greatly increasing gasoline yields.

A representative analysis of the gases separated is as follows:

Gas, mol. percent Methane 12.9 Ethan 6.9 Ethylene 5.9 Propan 13.8 Propylene 45.6 Butanes 2.9 Butylenes 10.7 Pentanes 1.3

From the above analysis it will be seen that the gases are more than unsaturated and that 73% of the gases are C: and C4 hydrocarbons.

A representative butane cut contained 31.3% isobutylene, 45.9% normal butylene and 22.8% isoand normal butane. This is a very impordrawn through line 23 after stabilization is as.

follows: (by volume) Percent Butanes 0.5

Butylenes 8.2 C5 hydrocarbons 26.3 C6 and heavier hydrocarbons 65.0

Lil

By altering the fractionation conditions the butyenes could, of course, be recovered with the C3 and C4 fraction of gases. of striking significance and important is the large percentage of C5 hydrocarbons. The pentane fraction is of an entirely different order than the pentane fraction obtained from the cracking of other stocks, and these hydrocarbons appear to be highly isomerized, i. e. to have a branched chain structure. More pentanes are produced than are required for the gasoline obtained from cracked wax and these excess pentanes may be blended with other motor fuel to improve the volatility characteristics and the anti-knock rating of winter gasolines.

The gas oil withdrawn through line 24 is a high gravity (44.8 A. P. I.) cycle stock which is amenable to further once-thru catalytic cracking or to thermal cracking or catalytic or thermal gas reversion. Ordinarily the gas oil from catalytic cracking is more amenable to thermal cracking than to further catalytic cracking, but the gas oil produced by the catalytic cracking of wax is highly suitable for charging to a catalytic cracking system.

The difference between the products formed by catalytically cracking wax and the products formed by thermally cracking wax or catalytically 0r thermally cracking other charging stocks cannot be over-emphasized. The octane number of the gasoline from the catalytically cracked wax is fully as high as that of gasoline from catalytically cracked gas oil even when the light ends are removed to give a product of 400 F. endpoint and a 10 pound per square inch Reid vapor pressure. Yet when this same wax is cracked thermally at 25 pounds at 975 F. with 20% cracking per pass, it gives a gasoline of only 55 octane number C. F. R. motor method. Thermally cracked gas oil gives a gasoline of 67 to '10 octane number C. F. R. motor method. Thus gasoline from thermally cracked wax has a much lower octane number than gasoline from thermally cracked gas oil, while gasoline from catalytically cracked wax gives a gasoline with a much higher octane number than gasoline from catalytically cracked gas oil, or an octane number equivalent to that of catalytically cracked gas oil even after the removal of light ends. The percentage of unsaturated hydrocarbons in debutanized gasoline from catalytically cracked wax is about 68.

The degree of unsaturation of the gasoline from low pressure once-thru thermal cracking of parafiin wax at low pressure was as high or higher than that of the various gasolines from catalytic cracking, and therefore it would appear that the higher octane number of the gasoline from the catalytic cracking of wax must be.

due to either: (1) more centrally located double bonds in the olefins, or (2) more highly branched or cyclicized carbon skeletons. If the effect were due to the location of the double bonds, hydrogenation would lower the octane number of gasoline from the catalytic and thermal cracking to the same level. Hydrogenation experiments have shown, however, that-hydrogenated gasoline from catalytic cracking does not produce as low octane numbers as are produced from the hydrogenation of thermally cracked gasolines. It therefore appears that the phenomenal results obtained by catalytically cracking wax are due not only to cracking but to the isomerization of the cracked products. Debutanized hydrogenated gasoline from catalytically cracked wax had an octane number of about 50, whereas from the best data obtainable, it appears that if gasoline from catalytically cracked wax consisted of straightchain hydrocarbons, then the octane number after hydrogenation would be about 3 C. F. R. motor method. Thus the isomerization of the gasoline constituents in gasoline from catalytically cracked wax'is an important feature of my invention.

Even in the case of gases I hav'e found a marked difierence in the products produced by the catalytic cracking of wax. Comparing fractions from thermal cracking, catalytic cracking of gas oil and catalytic cracking of wax:

The oleflnic hydrocarbons of low molecular weight, either those in the gas fraction or the gasoline fraction, may be separated from the paramnic fraction by the use of suitable selective solvents such as dichlorethyl ether, phenol, cresylic acid, nitrobenzene, furfural, etc., or they may be absorbed (hydrolyzed) in sulfuric acid and subsequently recovered therefrom. Alternatively, the olefins may be fractionated from the parafllns by azeotropic distillation or by superfractionation, i. e. using rectifying towers with a very large number of plates. For most purposes, however, the concentration of olefins is so high that such fractionation is not necessary.

In the catalytic cracking of wax hereinabove .described the cracking was effected in a 5-hour continuous run at 925 F. and a space velocity of same amount of carbon on the catalyst. Extrapolation of the data for 35 M. C. gas oil indicates that to obtain 40.7% gasoline in a 5-hour run at 925F., a space velocity of .14 would be required which would give a gas yield of 13% and a probable carbon deposition of 2% or more. The above data show the remarkable increase in cracking rates obtainable by the cracking of wax.

After a catalyst chamber has been on stream for the desired time, usually about 1 to 5 hours, the flow of hot vapors is stopped through that catalyst chamber, that particular catalyst chamber is cut out and the heated vapors are returned to another catalyst chamber. The first chamber is then regenerated in a conventional manner by blowing oxygen and oxygen-containing gas therethrough. This may be a flue gas introduced through line 25 and air introduced through line 26, these gases being forced by pump 21 through lines 28 and one of the lines 2! into the catalyst chamber i6. Combustion gases leave the chamber through one of lines II and are returned by line 3| for recirculation or for venting through line 3!. Suitable heating or cooling means may be employed in this regeneration system, and steam or other fluid may be charged with the oxygen-containing gas, as is well-known in the art. The regeneration of the catalyst is accomplished in the same way as the regeneration of the catalyst for the catalytic cracking of gas oils, and hence needs no further description.

The term wax" as used in this specification and in the accompanying claims is not limited to pure wax, but is hereby defined as including ordinary slack wax and oil-wax mixtures containing up to to of oil. The advantages of the invention are more pronounced, however, with wax which contains as small amount of oil as possible, preferably less than 50%.

While I have described in detail a preferred embodiment of my invention it should be understood that I do not limit myself to any of the details hereinabove set forth, except as defined by the following claims which should be construed as broadly as the prior art will permit.

I claim:

1. The method of converting wax into high quality motor fuel which comprises vaporizing and heating said wax to a temperature of about 850 to 1000 F., contacting the heated vapors with a catalyst comprising metal oxides at about atmospheric pressure to 50 pounds per square inch employing a space velocity of about $5 to 4 volumes (liquid basis) per volume catalyst space per hour, and fractionating the reaction products into at least one gas fraction, a gasoline fraction, and a fraction heavier than gasoline.

2. The method of claim 1 wherein the catalyst consists essentially of silica gel with a metal oxide deposited thereon.

3. The method of claim 1 wherein the catalyst comprises silica gel witha metal oxide of the class consisting of oxides of aluminum, cerium, thorium, cadmium, copper, nickel, manganese. and titanium deposited thereon.

4. The method of producing branched chain hydrocarbons containing about 4 to 8 carbon atoms, which comprises vaporizing a substantially straight chain paraffin wax, heating the vapors to about 850 to 1000 F. and contacting said vapors at said temperatures with a catalyst consisting essentially of alumina deposited on silica at a pressure of about atmospheric to 50 pounds per square inch and with a space velocity of about to 4 volumes of liquid charging stock per volume of catalyst space per hour.

5. The method of converting wax into high quality motor fuel which comprises vaporizing and heating said wax to a temperature of about 850 to 1000 F., contacting the heated vapors with a catalyst comprihing metal oxides and including alumina at super-atmospheric pressure and with a space velocity of about y to 4 volumes of wax (liquid basis) per volume of catalyst space per hour, and fractionating the reaction products into at least one gas fraction, a gasoline fraction and a fraction heavier than gasoline.

ERNESTW. 'rmnm. 

